Does leaving the car running on neutral charge the battery?

A) YES

B) NO



What makes you ask?

 

What's the point of gettting a Ferrari and having it sit around for days??? Shame on you!

 

Hello Peter, I wouldn't be too worried about it, I am reading that alot of people are using battery tenders to keep their batteries topped up while the car is sitting around, you will find most batteries drop off some voltage from just sitting idle. I might be an idea to purchase one of them to save you this drama in future? Next time you get a chance have a look at your battery electrolyte level, it might be a bit low or just mean your battery might be showing signs of needing replacing. By the sounds of your F1 light comming on the position 2, I would imagine because your engine is not running you haven't primed up the F1 system. Like you said all is good when you have the engine running

Make sure you get on the road more often when you can

 

On 308s, the Alternator needs 2,000 RPM to 'kick in' a switch for your dash light...if the cold-idle circuit is not working correctly, the car will not cold-idle at 2,000 rpm and your alternator light will NOT go out.....as far as the actual charging, that may still be going on, but if your battery is low along with low-idle you'll be waiting a LONG TIME before the alternator catches-up with what the battery needs to recharge.

For newer cars, this holds regardless of cold-idle level since the alternator is being driven by engine RPM - the primary load on the alternator during idle is engine ignition, not battery charging, so I would take some measurements to see what your alternator is doing, if anything, during idle.

 

Use of a tender avoids overloading the alternator...it's sized for running loads....not to recharge a battery from an major undervoltage condition....

Just the clock alone will drain a 308GTB pretty quickly.

 

I asked my Bosch rebuilder about this and was told that no the alt will charge at 800rpms per the spec for the 308. it may be a switch activated by another means or signal. I didn't look further into it.

 

I discourage my Dad from simply starting his cars in an attempt to charge their batteries.

My hunch is that more activation energy is required to start a sitting car than the amount of energy that can be gained after a car runs at idle for a few minutes.

In my opinion, the best way to protect a battery is either to disconnect the negative lead and let it sit or to keep it on a trickle charger.

 

308 Dash light is powered by a relay......over/under 12V is what it monitors.

 

You are right Dave, if you aren't going to use the car enough to drive the moisture from the oil via heat, it really does more harm than good, IMO.

 

Egads! I've finally learned what my problem is!

 

I am mystified. My 308 clock works real good. And, yet, I can leave the car for a couple weeks and it cranks right up. I generally drive it for 30 minutes to an hour or so once a week. I really don't have a schedule. Sometimes I drive it to work. No worries.

My Rx-7 on the other hand has suddenly developed some sort of super duper passive drain. Three years of no worries and now all of a sudden if I don't drive it for a week the battery is dang near dead. I replaced the battery. The car has a voltmeter that shows it charging near 14V. What gives?

Seamus

 

Seamus mine is the same way. In the winter it is on the lift unless the roads are free of salt/snow. I'll take it out then . I don't use a tender and my car will start right up even in 10-20* weather. Also my clock works but not well but it is correct twice a day. As to the dash ligh it goes out at around 1000rpm and when I look at my volt meter (I hooked one up in the car) it shows it is charging at idle (1000rpm). Getting about 13.5 volts . By the way I bought the battery in 2000 and it has 18k miles on it.

 

My Miata started doing exactly the same thing a few months back. After several tries, a new alternator and battery, we finally tracked down a badly corroded accessory ground. Replaced that, and like magic, she was like new again.

 

I'd put an ammeter inline with the battery and measure the current draw, then shut off accessories until you find out what is causing the current draw.(maybe radio, alarm etc going bad)

 

That's good work. Any tips on how to find it or did you just go through methodically cleaning up grounds? I do have some cause/effect in my case. An auxiliary fan was mounted to the A/C condensor and wired into the relay for the A/C in October. The fan only runs when the A/C is on but I suspect the hookup is somehow at the root of this problem.

FWIW... I tried measuring the drain by measuring amps from the battery negative post to the battery negative cable and only measured 0.01mv.

Seamus

 

Maybe you meant 0.01ma mv is millivolts, ma = milliamps

 

My rough rule of thumb is the car needs to be driven for twenty minites for each time its started just to recharge the battery to the point it was before starting.

If the battery has been drained by the clock, car alarm and any earth faults then it needs to be run longer.

A good automatic ,floating type battery charger will aleviate many problems by keeping your battery charged and in good condition when stored or not in use.

On the 308 you can also disconnect the neutral using the switch under the front hood, works well for longer storage, just remember to reset the clock when you reconnect it.

 

Yes, sorry, 0.01ma - milliamps. Doesn't sound like much.